title: The Arg-Gly-Asp motif in the cell adhesion molecule L1 promotes neurite outgrowth via interaction with the alphavbeta3 integrin.
abstract: The cell adhesion molecule L1 is a potent inducer of neurite outgrowth and it has been implicated in X-linked hydrocephalus and related neurological disorders. To investigate the mechanisms of neurite outgrowth stimulated by L1, attempts were made to identify the neuritogenic sites in L1. Fusion proteins containing different segments of the extracellular region of L1 were prepared and different neuronal cells were assayed on substrate-coated fusion proteins. Interestingly, both immunoglobulin (Ig)-like domains 2 and 6 (Ig2, Ig6) promoted neurite outgrowth from dorsal root ganglion cells, whereas neural retinal cells responded only to Ig2. L1 Ig2 contains a previously identified homophilic binding site, whereas L1 Ig6 contains an Arg-Gly-Asp (RGD) sequence. The neuritogenic activity of Ig6 was abrogated by mutations in the RGD site. The addition of RGD-containing peptides also inhibited the promotion of neurite outgrowth from dorsal root ganglion cells by glutathione S-transferase-Ig6, implicating the involvement of an integrin. The monoclonal antibody LM609 against alphavbeta3 integrin, but not an anti-beta1 antibody, inhibited the neuritogenic effects of Ig6. These data thus provide the first evidence that the RGD motif in L1 Ig6 is capable of promoting neurite outgrowth via interaction with the alphavbeta3 integrin on neuronal cells.
authors.affiliation: Banting and Best Department of Medical Research and Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1L6, Canada.
authors.forename: P M
authors.initials: PM
authors.lastname: Yip
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: A M
authors.initials: AM
authors.lastname: Montgomery
authors.forename: C H
authors.initials: CH
authors.lastname: Siu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D005727:Ganglia, Spinal / Q000166:cytology; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry; D039841:Leukocyte L1 Antigen Complex; D008969:Molecular Sequence Data; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016501:Neurites; D009474:Neurons / Q000166:cytology; D009842:Oligopeptides / Q000378:metabolism* / Q000494:pharmacology; D019030:Receptors, Vitronectin / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D012160:Retina / Q000166:cytology
chemical_list: D007136:Immunoglobulins; D039841:Leukocyte L1 Antigen Complex; D019006:Neural Cell Adhesion Molecules; D009842:Oligopeptides; D019030:Receptors, Vitronectin; D011993:Recombinant Fusion Proteins; C047981:arginyl-glycyl-aspartic acid